Lecture: Standard Model of Particle Physics€¦ · Schöning/Rodejohann 1 Standard Model of Particle Physics SS 2013 ... Tutorials offer the possibility to discuss open questions

Schöning/Rodejohann 1 Standard Model of Particle Physics SS 2013

Lecture: Standard Model of Particle Physics

(MVHE3)

Heidelberg SS 2013

W.Rodejohann (theorist)

+

A. Schöning (experimentalist)


Dr. Werner Rodejohann(Max-Planck Institut - Kernphysik)


Goal of this Lecture

● Theoretical and experimental introduction into the Standard Model of Particle Physics.

● Tutorials offer the possibility to discuss open questions and the

exercises.

● Content of Lecture:QED (Quantum Electrodynamics)

Electroweak Interactions and Unification

Electroweak Symmetry Breaking and Higgs Mechanism

(Strong Interaction)

Flavour Physics


Prerequisites

Requirements: PEP5 (Introduction to Particle Physics, bachelor) Particle Physics (Module MKEP1, master)

this course addresses master and graduate students

Other useful or related lectures: Theoretical Statistical Physics Quantum Field Theory Detector Physics Accelerator Physics


Credit Points

According to the Master Handbook the workload is 240 hourscorresponding to 8 credit points (ECTS)

Requirements Participation at Lectures and Tutorials Solve exercises (minimum score 50%)


Organisation

Lectures: Monday 16h15, Kleiner Hörsaal, Philosophenweg 12 Wednesday 11h15, Kleiner Hörsaal, Philosophenweg 12

Accompanying Tutorials: Tuesday (engl./germ.) : 9h15 INF227 SR2.402 (Julian Heeck) → first tutorial 30.4.

Thursday (engl.): 14h15 INF227 SR2.402 (He Zhang) → first tutorial 2.5.

Handout and return of exercises always Mondays after lecturefirst exercises handout 22.4.

More Information (e.g. literature) on the Web: http://www.mpi-hd.mpg.de/manitop/StandardModel/


Lecture Dates



give FEEDBACK!


Introduction:

“The Interplay betweenTheory and Experiment

in Particle Physics”


~50-60 years electron

proton

(neutron)

~1930


SM Lagrangian

~50-60 years electron

proton

(neutron)

~1930


Main Achievements in Theory

Relativistic Quantum Mechanics (QED, Dirac Equation)

Relativistic Quantum Field Theory (vacuum polarisation)

Gauge Theories (renormalisable field theory)

Electroweak Unification (electromagnetic+weak force)

Mass Generation and Spontaneous Symmetry Breaking

Quantum Chromodynamics and understanding of confinement

Standard Model of Particle Physics


Important Experimental Discoveries

Discovery of the muon (particle families)

Discovery of the pion (strong interaction)

Discovery of Parity Violation in Weak Interactions

Discovery of Strangeness and Fermion-Mixing

Discovery of the Neutrino

Observation of neutral currents (weak interaction)

Discovery of massive gauge bosons (W,Z)

Discovery of the Higgs boson at LHC in 2012

This all goes along with the development of modern particle detectors and accelerators


Interplay Theory-ExperimentPrediction of the Anti-electron (Dirac, 1928)Discovery of the Positron (Anderson, 1932)

Prediction of mesons (1935)Discovery of the muon (1936)Discovery of the pion (1947)

Prediction of the neutrino (Pauli 1930)Discovery of the electron neutrino (Cowan Reines, 1957)

Prediction of the muon neutrino (1950th)Discovery of the muon neutrino (Ledermann, Schwartz, Steinberger 1962)

Discovering the particle zoo (1960th )Development of Quantum Chromodynamics (1968)

Theory of Quark Mixing (1970th) …...


Anti-Particle Hypothesis

Paul Dirac (1928):

Field equation for a relativistic Quantum Mechanicsbased on Einsteins special relativity relation:

E2=m2

+ p2

Dirac equation has solutions for positively and negatively polarised particles and for positive and negative energies:

Later Feynman-Stückelberg interpretation:antiparticles are particles traveling in reverse time direction

negative energy: antiparticles!


Discovery of the Positron

Carl D. Anderson

Nobel Prize (1936)


Muon Discovery

Muon discovery incosmic rays by

Carl Anderson+

Seth Nedermeyer

Victor Hessdiscovery ofcosmic showers

Nobel Prize (1936)

1912


Theoretical Interpretation of themuon decay

μ- → e- ν ν Two neutrino hypothesis:

Energy spectrum of electrons from muon decay: μ- → e- ??

2-body decay3-bodydecay

Michel spectrum:m

μ =105.6 MeV

energy ofdecay electron


Theoretical Interpretation IIFurther studies of muon decays showed that e.g. μ→ e γ is forbidden

the muon is not an excited state of the electron

introduction of Lepton Family Numberμ- → e- ν

e ν

μ-

is allowed!


Discovery of the Electron-Neutrino

Discovery of the electron neutrino (Cowan, Reines, 1957)

Nobel Prize (1995)

Discovery of the muon neutrino (Ledermann,Schwartz,Steinberger 1962)

Nobel Prize (1988)

Anti-Electron-Neutrino


Prediction of the PionH.Yukawa predicted 1935 mesons as carriers of the strong force

Nobel Prize (1949)

meson mass ~ ħc / (range of force)

range ~ 1 fm → mmeson

= 200 MeV


Discovery of the Pion1947 discovered by Perkins, Ochialini and Powell

Nobel Prize (Powell 1950)

emulsions


Parity Violation in Weak Interactions

vector current:

jV =

axial-vector current:

j A =

5

∂ jV = 0 (conservation of currents)In Quantum Electrodynamics (QED)

Lorentz Structure of Weak Interactions?

scalar coupling:

S = ψψ

pseudoscalar coupling

P = ψ γ5ψ

j Lμ = 1/2 ( jV

μ− jAμ ) ≠

jRμ = 1/2 ( jV

μ + j Aμ )

Left-Right Symmetry broken if


Discovery of Parity Violation in Weak Decays

Nobel Prize

Co60 → Ni* e- ν-polarised

proposed by Lee + Yang

(also seen in muon decayLederman et al.)


Discovery of the StrangenessSurprise!

Production of Kaons and Lambda-Baryons in pp Collisions

“V-particles”

Long Lifetime! neither electromagnetic nor strong force


Prediction of the Charm Quark

ud ' = ud cosCs sinC cs ' = c

scosC−d sinC Neutral Current:

JNC = uΓu+ cΓc+ (dΓ d+ sΓ s)cos2ΘC+ (dΓd+ sΓ s)sin2

ΘC⏟Δ S=0

+ (dΓ s+ sΓ d−dΓ s− sΓd)sinΘC cosΘC⏟∣Δ S∣=1

flavor changing terms cancel out!

How explain non-observation of Flavor Changing Neutral Currents?

K →π γ

Add hypothetical c-quark

GIM suppression (Glashow, Iliopoulos, Maiani)


Observation of the Charm Quark

p Be → X J/Psi → X e+ e-

BNL: S.Ting et al. (1974)

e+ e- → J/Psi → e+ e- (μ+,μ-),(π+ π-)SLAC: B.Richter et al. (1974)

Nobel Prizes


Prediction of the Third Family

Mixing Matrix with three families (Kobayashi-Maskawa Matrix):

contains CP violation phase

C = charge conjugationP = parity operator

Sakharov: CP-Violation might explain observed matter-antimatterasymmetry in universe

third family needed! Nobel Prize (2008)

particle ↔ anti-particle


Discovery of the Third Family Tau Lepton discovered by MARK1 at SPEAR (1974-1976)

electron-muon problem: e + e−→ e +

μ− e + e−

→ e−μ+

explanation (M.Perl):

e + e−→ τ

+τ−

τ→ e ν ντ→μ ν ν

discovery of tau-lepton

(Reines et al.)

Nobel Prize (1995)

Discovery of the Bottom-Quark (1977) by M.Ledermann et al. at Fermilab


Prediction of Neutral Currents

Weak Neutral Currents, i.e. exchange of Z particles were predicted by Abdus Salam, Sheldon Glashow and Steven Weinberg 1973 (Standard Model)

Weak interaction described by SU(2) local gauge symmetry, which contains three fields W

1 , W

2 ,W

3 presented by the

physically observable fields W+ and W- and Z (neutral gauge boson)

Use neutrinos to test existence of the Z boson

Nobel Prize (1979)


Observation of Neutral Currents

Bubble ChamberGargamelle (1974)

νe e→νe eνe

e

Z

νe

e


Discovery of Z Gauge Boson

Rubia et al. (1983)

Nobel Prize (1984)

p p → (Z → e+ e-) X


Discovery of Z Gauge Boson

Rubia et al. (1983)

Nobel Prize (1984)

p p → (Z → e+ e-) X


Prediction of the Top MassRadiative Corrections:

e

e e

et

t

e+ e- collider LEP, Geneva


Discovery of the Top-Quark (1995)

Proton-Antiproton Collider1 x 1 TeV

Fermilab, USA

CDF + D0 Detectors

Top-Quark Mass ~172 GeV

CDF


Prediction of the Higgs Particle

Φ=ϕ0+ χ+ i ξ

minimum breaks symmetry: spontaneous symmetry breaking

χ

ξ

Introduce new (Higgs-) field to generate mass of fermions and bosons

Φ≠0


Prediction of the Higgs Mass

yellow region excluded by LEP blue chi2 curve from radiative corrections

Status after LEPand before

Tevatron + LHC


Search for the Higgs BosonMain Problem:

SM Higgs Mass is not predicted by theory only weakly constrained by precision measurements

Have to look in a large mass range:

Higgs decays:


Large Hadron Collider (CERN)

26.7 km circumference!

LHC (pp) 7-8 (14) TeV in 2011/12


The Discovery of the Higgs-Boson


Compatibility of ATLAS data to No-Higgs Hypothesis


Higgs Exclusion Plot

there is only one SM-Higgs


Compilation of Signal Strenghts in Various Decays

July 2012

Really THE SM-Higgs?


The Unknown Mass Hierarchy of Neutrinos

from neutrino oscillation only squared mass differences known!


from Y. Nakajima

Last Neutrino-Mixing Angle Measured in 2012

Missing: CP-Phase δ in lepton matrix (25th parameter of νSM)

from T. Schwetz-Mangolt

Mixing angle Theta13

CP-Phase δ


Summary

Standard Model seems to be fully established Big triumph of particle physics theory and experiment

But many fundamental questions not addressed by SM!(fermion generations, matter-antimatter asymmetry, dark matter, gravitation, ...)


Documents

Lecture: Standard Model of Particle Physics€¦ · Schöning/Rodejohann 1 Standard Model of Particle Physics SS 2013 ... Tutorials offer the possibility to discuss open questions